Research On Enhancing Photoelectrochemical Water Splitting Activity Of Hemitate Photoanode By Noncontact Photonic Crystal Film

To many thin film photoelectrodes for water splitting,solving the trade-off problem between light absorption and charge collection has always been a challenge.Although the uses of metallic back-reflector,antireflection coating,and textured substrate and light absorber enable the improvement of light utilization efficiency,these methods still suffer from high cost,complex fabrication process,especially,incompetent separation of photogenerated carriers.Since photonic crystals have a periodic dielectric composition structure,they can effectively control incident light and exhibit unique optical characteristics.They have the characteristics of reflected light,captured light,and slowed down light.Therefore it is highly desirable to apply the photonic crystals to light energy related fields.But so far,there are mainly two ways to use photonic crystals to improve the performance of PEC.Either light absorbers are directly made into photonic crystal-like structures or materials are grown or attached to the surface of photonic crystals.The two methods need consider the matching degree of the electronic structure between the light absorber and the photonic crystal film or select a proper template.Rational design of non-contact photonic crystal films can avoid the above problems.In this dissertation,taking hematite??-Fe₂O₃?photoanode as a model long-range ordered photonic crystal films and short-range ordered photonic crystal films were synthesized,which were futher used to enhance PEC performance of the photoelectrodes.The main work is as follows:?1??-Fe₂O₃ nanorod film photoanode was synthesized by hydrothermal method and long-range ordered photonic crystal?PC?film consisted of silica nanoparticles and ethoxylated trimethylolpropane triacrylate?ETPTA?resin was synthesized by a colloidal self-assembly route.?-Fe₂O₃-PC photoanode was fabricated through a non-contact manner.The products were characterized by FE-SEM,TEM,XRD,XPS,PL and other characterization methods.Specifically,more than 250 m V cathodic shift of onset potential and 4-times larger photocurrent at 1.0 V vs.RHE were achieved over the?-Fe₂O₃-PC photoanode hybrid system,compared with pristine?-Fe₂O₃photoanode.It was showed that PC film not only boosted light absorption of?-Fe₂O₃layer but also improved its photoconductivity.These new findings will open a new avenue to design high-performance solar energy conversion device.?2?A short-range ordered photonic crystal film?APC?composed of aminated silica nanoparticles was prepared by controlled colloidal self-assembly.The angle-independent and short-range ordered photonic crystal film was used in a non-contact manner to enhance the PEC activity of?-Fe₂O₃ nanorod films synthesized by hydrothermal method in a non-contact manner.The results showed that at a potential relative to 1.0 V vs.RHE,the?-Fe₂O₃-APC film photoanode exhibits a photocurrent density of 0.46 m A/cm²,which is 4 times that of the?-Fe₂O₃ nanorod film.The potential onset of?-Fe₂O₃ was negatively shifted by approximately 180 m V.APC film not only improves the light absorption of hematite but also promotes the effective separation of photo-generated carriers.This finding that APC films with strong scatting ablity can enhance the performance of PEC will provide new ideas for more researchers.